Audiovisual annunciator with priority ranking for each condition

ABSTRACT

An audiovisual annunciator for warning a system operator of the occurrence of various monitored conditions within the system. A signal generated in response to the occurrence of a monitored condition energizes an associated warning lamp to visibly indicate that the condition has occurred. An audio signal is simultaneously generated and acoustically transmitted to the system operator. A logic circuit assigns a priority ranking to each condition, such that, when several conditions occur simultaneously, an audio signal is generated for only the highest priority condition. If the operator acknowledges the highest priority annunciated condition, an audio signal is transmitted for the next highest priority occurring condition. The operator may recall a silenced warning so long as the condition continues to exist. A switch permits the operator to test the warning lamps, the priority circuitry, and the audio circuitry.

United States Patent [72] Inventor Svtmge Furs! 3,015,702 1/1962 Vogel et al 179/1002 Costa Mesa, Calif. 2,917,731 12/1959 Rodgers 340/214 [21] Appl. No. 770,941 3,199,081 8/1965 Kok et a1. 340/183X [22] Filed 1968 Primary Examiner-Stanley M. Urynowicz, Jr. [45] Patented June 1, 1971 A O & o [73] Assignee Master Specialties Company tomey Costa Mesa, Calif.

H H I ABSTRACT: An audiovisual annunciator for warning a s4 AUDIOVISUAL ANNUNCIATORVITR midi-i? 3P? P$I A" E flltlons W] In efsystem. I Slfjn In {esponse i cums, 8 Dams m e occurrence 0 a monltore con man energ zes associated warning lamp to VlSlbly indicate that the condition U.S. Clam; has occurred An audio signal is simultaneously generated and 9/ l 3 /2 495i! acoustically transmitted to the system operator. A logic circuit [51] int. Cl. ..G08b 19/ 0, assigns a priority ranking to each condition, such that, when q several conditions occur simultaneously, an audio signal is Field 0 generated for only the highest conditio Ifthe opera- -2 E 27, 412, 183 tor acknowledges the highest priority annunciated condition,

an audio signal is transmitted for the next highest priority oc- [56] References c'ted -curn'ng condition. The operator may recall a silenced warning UNITED STATES PATENTS so long as the condition continues to exist. A switch permits 2,804,501 8/1957 Hart 340/27X the operator to test the warning lamps, the priority circuitry, I 2,934,752 4/1960 Arrasmith 340/27 and the audio circuitry.

20 MC. DRIVER TAPE 1 TA P E A N D MOTO R LAMP CARTRIDGES POWE R 5 U P PLY 5|GNAL AU 10 AUDIO mu i 1,9553, SWITCHING AMPL! FIER mo AMPLlFlERS TRANSDUCER CONT 0L LAMP CAUTlON R L M PS PANEL DRIVERS A PATENTED Jun 119?:

sum 1 or 7 MCDRIVER AND mg L TAPE. LAMP CARTRIDGES /7 W /5 POWER SUPPLY /J 7 5mm Lam Aumo AUDIO o I swmnma AMPLIFIER AND f AMPLIHERS TRANSDUCER CONTROL I LAMP cAUTwN PANEL DRIVERS LAMPS I NVENTOR:

SI ENAABE F0552".

ATTJS.

' PATENTED JUN 1197:

SHEET 3 BF 7 INVENTOR: SI/ENAAEE FUR s T.

.ATTYS.

PATENIED JUN 1197:

SHEET 7 UF 7 ATTYEI.

AUDIOVISUAL ANNUNCIATOiR WITH PRIORITY RANKING FOR EACH CONDITION BACKGROUND OF THE INVENTION This invention relates generally to an improved warning system, and, more particularly, to an annunciator for acoustically and visibly warning an aircraft pilot of the occurrence of various monitored conditions within the aircraft.

At the present time a number of different visual annunciators are available for aircraft, aerospace, military, industrial, and commercial applications. A typical visual annunciator includes a caution panel having a large number of word-indicator lights. Each light is connected to a sensing device which is responsive to the occurrence of a particular condition within the monitored system and each light has a legend indicative of the related condition. When a monitored condition malfunction occurs, the associated word-indicator light is energized to visibly announce the occurrence of the condition.

When the annunciator is used in aircraft, there may be several additions. A circuit is usually included to permit the pilot to dim the indicator lights during night flying. Furthermore, since space limitations usually require mounting the caution light panel at the pilots side, a single large red master caution light is located on the aircraft control panel in front of the pilot to attract the pilots attention when a monitored condition occurs. When one or more of the monitored conditions occur, the master caution light is either turned or flashed. A switch on the caution light panel permits the pilot to acknowledge the occurrence of a condition, thereby extinguishing the master caution light. The master caution light will remain extinguished until either a different one of the monitored conditions occurs or the monitor is reset.

Attempts have been made to develop an annunciator for audibly warning a system operator of a source of trouble in the system and, possibly, for audibly stating corrective steps to be taken by the system operator for eliminating the source of trouble. Audio annunciators to date frequently have been unreliable and in many instances lack priority circuits, and therefore are not suitable for many uses, such as in aircraft. The prior art audio annunciators typically lock onto the channel for the first occurring condition, even though the condition is not as critical as a subsequently occurring condition. In some cases, the audio annunciator remains locked onto the channel for the first occurring condition until reset by the operator, even after the condition has been corrected. Another type of prior art audio annunciator has a relay for each condition sensed. The highest priority sensed condition blocks the relays for all lower priority conditions. As long as a high priority condition exists, a lower priority condition cannot be annunciated. There is no provision for the operator to acknowledge an annunciated condition so that a simultaneously occurring lower priority condition can be annunciated.

With the increased use of aircraft, and especially helicopters, for combat applications, the demand for a highly reliable, compact audiovisual annunciator has been intensified. Under combat conditions a helicopter pilot is called upon to operate guns as well as to navigate and pilot the helicopter. Even if the pilot notices that the master caution light has come on, he may not have time to look at the caution panel to determine what condition has occurred and to decide what corrective steps should be taken. An audiovisual annunciator will solve this problem by audibly telling the pilot that a condition has occurred and then telling him what corrective steps should be taken.

SUMMARY OF THE INVENTION to each condition sensing device. Whenever a condition is sensed, the associated channel switches on a caution lamp which 5 mounted on a caution panel. The caution panel contains a caution lamp for each channel, each lamp being of the word-indicator type bearing a legend indicative of the condition sensed by the associated device.

Each channel is assigned a priority ranking consistent with the critical nature of the condition sensed by the connected condition sensing device. Logic circuitry within each channel generates an inhibit signal in response to either a signal from the associated condition sensing device or an inhibit signal from the next higher priority channel. Thus, when a condition is sensed by a device, the associated channel produces an inhibit signal and, as a consequence, all channels having lower priorities produce inhibit signals. The inhibit signal from the lowest priority channel is used to operate a master caution light, which is mounted in a conspicuous location, and may additionally be used to operate a flashing light on the caution panel.

A tape cartridge having an endless prerecorded tape and a pickup head is associated with each channel. The tape cartridges are simultaneously driven from a single motor driven capstan. The motor is operated from a regulated power supply which is-turned on in response to an inhibit signal generated by the lowest priority channel. The output of each pickup head is connected to the input of a normally off switching amplifier. The switching amplifier connected to the tape cartridge for the highest priority channel producing an, inhibit signal is turned on to pass and amplify the signal from the connected pickup head. Since only one switching amplifier is on at a time, the outputs of all switching amplifiers can be connected to parallel and fed to the input of an audio amplifier. The output of the audio amplifier may be connected to a speaker system or to an existing communication system, such as the pilots intercom system when the annunciator is used in an aircraft.

An acknowledging circuit is provided to allow the operator to silence the audio portion of the annunciator. When the operator momentarily pushes a silencing switch on a control panel, the inhibit signal from the highest priority channel generating an inhibit signal is silenced. As a result, the associated switching amplifier is turned off and the switching amplifier for the next highest priority channel generating an inhibit signal is turned on. If none of the other channels is generating an inhibit signal, all switching amplifiers and the power supply for the tape drive motor are turned off since an inhibit signal will not appear at the output of the lowest priority channel. Each channel includes a memory which is set when the channel has been silenced and which will remain set as long as a condition continues to be sensed by the associated device. A recall circuit is provided to allow the operator to recall the highest priority silenced inhibit signal by clearing all set memories.

The control panel also contains an audio off switch which, when in the off position, turns of? the power supply for the tape drive motor and blocks the acknowledging circuit. Thus, as long as the audio is turned off, the operator cannot silence a channel and therefore cannot turn the master caution lamp off. Still another switch on the control panel permits the operator to selectively test either the caution lamps or the audio and logic circuitry. When the switch is in the lamp test" position and the caution lamps are working properly, all of the caution lamps on the caution panel are turned on. When the switch is in the audio test" position, all of the sensed conditions are simulated. The audio circuitry, logic circuitry and acknowledging circuitry for each channel are then tested, sequentially according to the priority of each channel, by successively operating the silence switch.

Accordingly, it is an object of this invention to provide an improved audiovisual annunciator for warning a system operator of the occurrence of monitored conditions within a system.

Another object oftthis invention is to provide an audio annunciator giving instant transmission of a warning of higher priority than the one that might be in progress.

Still another object of the invention is to provide an audio annunciator in which the transmission of a warning may be silenced, permitting a lower priority warning to be transmitted.

Another object of the invention is to provide an audio annunciator in which a silenced warning, of higher priority than a warning in progress, may be recalled as long as the condition associated with the higher priority warning continues.

Still another. object of the invention is to provide an improved test circuit for an audiovisual annunciator.

Other objects and advantages of the invention will become apparent in the following detailed description of a preferred form thereof, reference being had to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an audiovisual annunciator constructed in accordance with the instant invention;

FIG. 2 is a schematic diagram showing the signal conditioning circuitry, the control circuitry and the logic circuitry for one channel, with the channel shown in a normal state;

FIG. 3 is a schematic diagram of the tape drive motor and capstan, the tape cartridges and the audio-switching amplifiers;

FIG. 4 is a schematic diagram of the regulated power supply for the tape drive'motor and the master caution lamp driver;

FIG. 5 is a schematic diagram similar to FIG. 2, but showing the channel in a condition sensing state;

FIG. 6 is a schematic diagram similar to FIG. 2, but showing the channel in a condition sensing state as the silence switch is operated;

FIG. 7 is a schematic diagram similar to FIG. 2, but showing the channel in a silenced condition sensing state as the recall switch is operated; and

FIG. 8 is a schematic diagram similar to FIG. 2, but showing the channel in a normal state as the audio circuitry is tested.

DESCRIPTION OF THE PREFERRED EMBODIMENT For convenience, the annunciator shown and described is a ZO-channel audiovisual annunciator designed for use in an aircraft, although the number of channels and the use are not intended to be restricted to this. Referring now to FIG. 1, a flow diagram for an audiovisual annunciator constructed in accordance with the instant invention is shown. The heavy black lines connecting the various blocks in FIG. 1 represent a separate connection for each of the 20channels while the lighter black lines represent either a single connection or a number of connections for the different controls, and the dashed line represents a mechanical linkage.

Each channel includes a signal conditioner 11, a logic circuit 12, a lamp driver 13, one or more caution lamps 14, a tape cartridge having an endless prerecorded magnetic tape and a pickup head, and a switching amplifier 16. Each of the signal conditioners 11 is connected to a different condition sensing device, which is built into the aircraft or other monitored system. Each condition sensing device generates a signal in response to a. different sensed condition, for example, a signal in response to a different sensed condition, for example, a signal may be generated when the fuel is low, when the landing gear is down, or when the oil pressure in an engine is low. Since the various types of conditions sensing devices may produce different types of signals, each channel has signal conditioner 1-1 for converting the signal produced by the connected device to a uniform logic signal, namely, to a logic one or voltage for no signal and a logic zero or ground for a signal.

Each of the signal-conditioning circuits 11 is connected to a logic circuit 12. Whenever an input to a logic circuit 12 is grounded by the associated signal conditioner 11 in response to a sensed condition, the logic circuit 12 switches on a lamp driver 13 to turn on a related caution lamp 14. The caution lamps 14 for all channels are mounted in a group on a caution panel and are of the word-indicator type, each lamp 14 having a legend indicative of the sensed condition which causes the lamp to be turned on. A caution lamp 14 will remain on as long as the related condition exists.

The 20 logic circuits 12 are assigned priorities according to the critical nature of the various sensed conditions. Each of the logic circuits 12 generates an inhibit signal in response to either a signal from the connected signal conditioner 11 indicating that a condition has been sensed or an inhibit signal from the next higher priority channel. Thus, when a condition is sensed, the related channel and all channels having lower priorities generate inhibit signals. The logic output of the lowest priority channel is used to turn on a master caution driver and lamp 17 and a power supply 18 for operating a tape drive motor 19, whenever an inhibit signal is generated in the lowest priority channel. The tape drive motor 19 drives a single'capstan 20 for simultaneously operating the 20 tape cartridges 15. Each tape cartridge 15 includes a pickup head for producing an audio signal when the tapes are driven. The 20 pickup heads are connected to the inputs of the 20 normally off audio switching amplifiers 16. Each logic circuit 12 is also connected to an associated switching amplifier 16. The switching amplifier 16 connected to the highest priority logic circuit 12 which is generating an inhibit signal is turned on to amplify and pass an audio signal from the related tape cartridge 15. Since, at the most, only one of the switching amplifiers 16 is on at one time, the outputs of the 20 switching amplifiers 16 are connected in parallel and fed to the input of a conventional audio amplifier and transducer 21. In the case of an aircraft, the audio amplifier and transducer 21 may be the pilot's intercom which is already built into the aircraft.

A control panel 22 is connected to all of the logic circuits 12. The control panel 22 includes a lamp and audio test switch, a silence switch, a recall switch, an audio off switch, and a conventional caution lamp dimmer switch. The operation of the various controls will be described in greater detail later.

Referring now to FIG. 2, the various controls on the control panel 22 are shown along with the signal conditioner 11, the logic circuit 12, the lamp driver 13, and the caution lamps 14 for the highest priority channel. The circuitry relating to the highest priority channel is shown enclosed within the dashed line 23, while the various controls are shown above the enclosed dashed line 23 and a portion of the second highest priority channel is shown in dashed lines to show the serial and parallel connections between channels.

Each channel has a number of terminals 24 which are connected in common to a conventional regulated power supply (not shown). When commercially available logic elements are used, the power supply may, for instance, have a regulated 5- volt output. The numerous logic elements used in each channel are NAND gates. Each NAND gate has a logic zero output, i.e., a grounded output, whenever all of the gate inputs are a logic one, i.e., at the regulated voltage supplied to the terminals 24. The NAND gates will have a logic one output whenever at least one of the gate inputs is a logic zero.

The different states of the logic circuits 12 are represented in FIGS. 2 and 5--8, with the ground potential leads shown in heavy black and the high potential leads shown in a lighter black.

The signal conditioner l 1, which is shown at the left of the channel, includes a resistor 27, a diode 28 and a capacitor 29. The resistor 27, the diode 28 and the capacitor 29 are connected in parallel between the power terminal 24 and a terminal 30. The condition sensing device is shown as a normally open switch 31 which grounds the terminal 30 when a condition is sensed. With this arrangement, the terminal 30 is normally at the voltage of the power terminal 24 and is grounded when a condition is sensed. The diode 28 and the capacitor 29 are included to reduce transients when the switch 31 is opened and closed.

The terminal 30 is connected to one input of a NAND gate 32 while the other input to the NAND gate 32 is connected to an audio test line 33, which is normally at the potential of the power terminal 24. The NAND gate 32 will have a grounded output except when the switch 31 is closed by a sensed condition or when the audio circuitry is being tested. The output of the gate 32 is connected in parallel to the inputs of two NAND gates 34 and 35. The two gates 34 and 35 normally have high potential outputs since they each normally have at least one grounded input. The normally high output of the gate 35 is connected invparallel to the inputs of two NAND gates 36 and 37. The power terminal 24 is connected to the other inputs of the two gates 36 and 37 so that the outputs of the two gates 36 and 37 are normally grounded. The normally grounded output of the gate 36 and the power terminal 24 are connected to a NAND gate 38, which has an output terminal 39. The output terminal 39 is normally at a high potential and is grounded when the switch 31 senses a condition. The output terminal 39 for each channel is connected to an audio-switching amplifier 16, turning on the switching amplifier 16 when the output 39 of the gate 38 is grounded.

The normally grounded output of the gate 37 and the power terminal 24 are connected to the two inputs of a NAND gate 40. The output 41 of the gate 40 is connected in parallel to the inputs to two gates 37 and 38 located in the next lower priority channel. The two gates 37 and 38' correspond to the two gates 37 and38 in the highest priority channel. The chief difference between the highest priority channel and the lower priority channels is that the gates 37 and 38 in the highest priority channel each have an input connected to the power terminal 24, while the gates 37' and 38' in each lower priority channel have corresponding inputs connected to the output 41 of the gate 40 in the adjacent, higher priority channel. Therefore, the gate 37 in the highest priority channel will have two positive inputs and a negative output whenever the channel is in a normal state while the corresponding gate 37" in each lower priority channel has two positive inputs and a negative output only when the channel and all higher priority channels are in normal states. The output 41 of the gate 40' for the lowest priority channel is positive only when all channels are in normal states. Similarly, the gate 38 in each lower priority channel will have a positive input from the output 41 of the gate 40 in the next higher priority channel whenever all higher priority channels are in normal states and each gate 38' will normally have a negative input from the associated gate 36. If a gate 38' has a positive input from the output 41 of the gate 40 in the next higher priority channel and a positive input from the gate 36' because of a sensed condition, then the output terminal 39' will be grounded to turn on the associated audio-switching amplifier 16. However, if a higher priority channel subsequently senses a condition, then the gate 38' will have a high output 39' and the associated switching amplifier 16 will be biased oft".

The NAND gate 34 has a normally grounded input from the gate 32 and a normally high input from the audio test line 33. The output of the gate 34, which is high except when a condition is sensed by the switch 31 and the audio test line 33 is in the normally high state, is connected to one input of a NAND gate 42. The NAND gate 42 has two additional normally high inputs, one connected to the output terminal 39 of the gate 38 and the other connected to a lamp test line 43. The normally grounded output of the gate 42 is connected to the lamp driver 13, which includes a resistor 44 and a transistor 45. The resistor 44 is connected between the output of the gage 42 and the base of the transistor 45. A high voltage power source, for example, the 28-volt power source available in an aircraft, is connected between a terminal 46 and ground. The terminal 46 is connected through a current limiting resistor 47 and one or more caution lamps 14 to the collector of the transistor 45, while the emitter of the transistor 45 is grounded. As long as the output of the gate 42 is grounded, the transistor 45 is biased off. However, when one of the inputs to the gate 42 is grounded, the output of the gate 42 will be at the voltage of the power terminal 24, switching on the transistor 45 to energize the caution lamps 14. Two caution lamps 14 are shown in parallel for safety purposes, since incandescent lamps are inherently subject to failure, but the statistical chance of both lamps failing at the same time is very low.

The remaining portions of FIG. 2 will be described in detail in describing the various modes of operation, as shown in FIGS. 5-8.

Referring now to FIGS. 2 and 3, the audio portion of the annunciator is shown in detail. The single-elongated capstan 20 is rotated by the tape drive motor 19 whenever power is applied to a terminal 50 on the motor 19 by the power supply 18. 20 tape cartridges 15, one for each channel, are mounted on a holder to simultaneously, engage the capstan 20. Each cartridge 15 includes a prerecorded endless tape and a pickup head 51. Problems with pickup head alignment are eliminated since the pickup heads 51 are permanently mounted within the cartridges 15. The output of each pickup head 51 is connected through a DC blocking capacitor 52 to the base of a transistor 53. The proper bias is maintained on the base of each transistor 53 by a voltage divider, including a resistor 54 connected between the power terminal and the base of the transistor 53 and a resistor 55 connected between the base of the transistor 53 and ground. A resistor 56 is connected between the power terminal 24 and an audio output terminal 57, which is also connected in parallel to the collectors of the 20 transistors 53 The emitter of each transistor 53 is connected through a bypass capacitor 58 to ground and through a resistor 59 to the output terminal 39 of the NAND gate 38 for an associated channel. Since the output terminals 39 are normally high, the transistors 53 are all biased off. However, when one or more conditions are sensed, the output terminal 39 for the highest priority condition sensing channel is grounded. The grounded output terminal 39 turns on the transistor 53 in the associated switching amplifier 16 to amplify and pass an audio signal from the associated pickup head 51 to the audio output terminal 57. Since at the most only one of the switching amplifiers 16 is on at any given time, only one resistor 56 is needed between the power terminal 24 and the parallel collectors of the transistors 53. As previously stated, the common audio output 57 of the switching amplifiers 16 is connected'to the input of a conventional audio amplifier and transducer 21.

Referring now to FIG. 4, the master caution lamp driver 17 and the regulated power supply 18 for the tape drive motor 19 are shown in detail. Both the driver 17 and the power supply 18 are operated from the terminal 46 of the available high voltage power source. The driver 17 comprises a switching transistor 61 connected in series between the power terminal 46 and an output terminal 62 and related circuitry for controlling the conduction of the transistor 61. When the transistor 61 is conducting, current flows between the collector, which is connected to the power terminal 46, and the emitter, which is connected to the output terminal 62, to energize a master caution lamp 63 and other optional devices such as a flashing caution lamp (not shown) which may be located on the control panel 22. The driver 17 has three inputs for switching on the transistor 61 upon the occurrence of any of three conditions. One input terminal 64 is connected either directly or through a driver (not shown) to the output 41' of the NAND gate 38' in the lowest priority channel. The additional driver stage may be required to handle the current load. The input terminal 64, which is normally high and is grounded when a condition is sensed in any of the 20 channels, is connected through an isolation diode 65 to the base of a transistor 66. The outer two input terminals 67 and 68 are also connected through isolation diodes 69 and 70, respectively, to the base of the transistor 66. The terminal 67 is connected to an audio off line 71 (FIG. 2) which is normally at the voltage of the power terminal 24. When the audio circuitry is turned otf', the audio off line 71, and hence the input terminal 67 is grounded. The other input terminal 68 is connected to a terminal on a two-way test switch 72 (FIG. 2) which is grounded while the audiocircuitry is tested.

A resistor 73 connects the base of the transistor 66 to the' power terminal 46 and a second resistor 74 connects the base to ground. The two resistor 73 and 74 form a voltage divider to bias the transistor 66 in a normally conducting state. The emitter of the transistor 66 is connected to ground through a diode 75, while the collector is connected to the base of a transistor 76. The diode 75 biases the transistor 66 off when one of the input terminals 64, 67 and 68 is grounded, compensating for the voltage drop across the diodes 65, 69 and 70. A bias resistor 77 is connected from the power terminal 46 to the collector of the transistor 66. With this arrangement, the transistor 66 is normally conducting. However, when one or more of the input terminals 64, 67 and 68 are grounded, the base of the transistor 66 will also be grounded, switching the transistor 66 to a nonconducting state.

When the transistor 66 is nonconducting, the voltage on the base of the transistor 76 will rise. The emitter voltage of the transistor 76 will rise as the base voltage increases, since the transistor 76 is connected in an emitter follower arrangement. The emitter of the transistor 76 is connected to the base of the switching transistor 61 to control the conduction of the transistor 61. The transistor 61 will conduct when its base voltage is high and will be nonconducting when its base voltage is low. A resistor 78 is connected between the power terminal 46 and the collector of the transistor 76 while a resistor 79 is connected between the output terminal 62 and the common connection between the emitter of the transistor 76 and the base of the transistor 61 to maintain a proper bias on the transistors 76 and 61. A resistor 80 is connected between the output terminal 62 and ground to bias the transistor 61.

The regulated power supply 18 for the tape drive motor 19 is similar to the driver 17, with the addition of a voltage reference. A control transistor 83 is connected in series between the high voltage power terminal 46 and the terminal 50 on the tape drive motor 19 (see FIG. 3). The collector of the transistor 83 is connected to the power terminal 46 while the emitter is connected through an isolation diode 84 to the terminal 50 and the base is connected to the emitter of a transistor 85 which serves as a DC amplifier in a regulated current source. The power supply 18 has two control inputs. In addition to being connected to the driver 17, the input terminal 64 is'connected through an isolation diode 86 to the power supply 18. The terminal 64, which is normally at the potential of the power terminal 24, supplies the base voltage to a transistor 87 through a voltage divider comprising resistors 88 and 89. The emitter of the transistor 87 is connected through a biasing diode 90 to ground and the collector is connected through a resistor 91 to the power terminal 46. The collector of the transistor 87 is connected to the base of the transistor 85. A voltage reference comprising a Zener diode 92 in series with one or more diodes 93 (the number of diodes 93 is selected to give the desired reference voltage) is also connected from the base of the transistor 85 to ground.

As long as the terminal 64 is at its normally high voltage, the transistor 87 will conduct and a low voltage will appear on the base of the transistor 85. When a condition is sensed in one or more channels, the terminal 64 will be grounded, causing the transistor 87 to become nonconducting, and the reference voltage will be applied to the base of the transistor 85. A second input terminal 94, connected between the isolation diode 86 and the resistor 88, is connected to a normally open terminal on an audio-off switch 95 (FIG. 2). When the switch 95 is in the audio-off position, the power terminal 24 is connected to the terminal 94 to maintain the transistor 87 in a conducting state, regardless of the states of the logic channels.

As staged above, when the transistor 87 is turned off, the reference voltage determined by the Zener diode 92 and the diode 93 is applied to the base of the transistor 85. A resistor 95 is connected between the power terminal 46 and the collector of the transistor 85 while the emitter of the transistor 85 is connected to the base of the control transistor 83 and to the resistor 96, which is connected to the emitter of the transistor 83. The transistor 85 is connected in an emitter follower arrangement to supply a constant current to the base of the control transistor 83, regardless of fluctuations in the voltage at the power terminal 46. A resistor 97 is connected between the emitter of the control transistor 83 and ground, to bias the transistor 83. A diode 98 is placed between the terminal 50 and ground to reduce any transients which the tape drive motor 19 might produce.

Turning now to FIGS. 5-8, the operation of the logic circuits l2 and the controls is shown in detail. FIG. 5 shows the circuit of FIG. 2, but with the highest priority channel sensing a condition. The switch 31 is closed by the sensed condition to ground one of the two high inputs to the NAND gate 32. When one input to the gate 32 is grounded, the gate 32 will have a high output, which will cause both the gate 34 and the gate 35 to have grounded outputs. The grounded output of gate 34 causes the NAND gate 42 to have a high output, which biases the transistor 45 into a conducting state. If the transistor 45 is conducting, the associated caution lamps will be energized by a current flowing from the high voltage power terminal 46, through the resistor 47, the parallel caution lamps 14, the collector of the transistor 45, and from the emitter of the transistor 45 to ground. The grounded output of the gate 35 will cause the gate 37 to have a high output. Since two high inputs are now applied to the gate 40, the gate 40 will now have a grounded output 41 which is connected to the gates 37 and 38 in the next lower priority channel. The gate 37 will now have a high output, regardless of whether a condition is sensed by the channel in which the gate 37 is located. The gate 40 will now have to high inputs and a grounded output 41' which is fed to the next lower priority channel. Since the channels are serially connected, the corresponding output 41 for each channel will be grounded. The grounded output 41 for the lowest priority channel is connected to the terminal 64 (FIG. 4) to turn on the master caution lamp driver 17 and the power supply 18 for operating the tape driver motor 19.

The grounded output of the NAND gate 35 in the highest priority channel is also connected to the gate 36, switching the output of the gate 36 to a high state. The gate 38 now has two high inputs and a grounded output 39 which turns on the associated switching amplifier 16 (FIG. 3). Since the grounded output 41 of the gate 40 is connected to the corresponding gate 38 in the next lower priority channel, the output 39 of the gate 38' will be high, regardless of whether a condition is sensed by the associated channel. Since all corresponding outputs 39' for the lower priority channels high, all of the corresponding switching amplifiers 16 for the lower priority channels will be turned off.

The operation of the silencing circuitry is shown in FIG. 6. As in the previous figures, heavy lines are used to represent grounded or logic zero leads while light lines are used to represent high voltage or logic one leads. Diagonal marks have been placed in FIG. 6 to indicate leads which change state when a silence switch 100 is momentarily operated. The power terminal 24 is connected through a pair of parallel resistors 101 and 102 to the set" and reset terminals of a flipflop 103. When the silence switch 100 is in the normal position, the reset terminal of the flip-flop 103 is grounded and the set terminal is at the potential of the power terminal 24. While the silence switch is momentarily operated, the set terminal of the flip-flop 103 will be grounded and the reset terminal will be at the high potential. The Q or normally high output of the flip-flop 103 is connected through a bias resistor 104 to the base of a transistor 105. The power terminal 24 is connected through a resistor 106 to the collector of the transistor while the emitter of the transistor 105 is grounded. The transistor 105 is normally conducting since its base is normally high through the resistor 104. A silence line 107, connected to the collector of the transistor 105, will be grounded or a logic zero as long as the transistor 105 conducts. The silence line 107 is connected in parallel to the inputs of NAND gates 108 in each logic channel. Thus, when the silence switch is operated, the input to the NAND gate 108 is momentarily high. The other input of the NAND gate 108 is connected to the normally high output of a silence flip-flop 109, and the output of the gate 108 is connected to the clock input of the flip-flop 109. The flip-flop 109 also has an input connected to the output terminal 39 of the gate 38. The normally grounded output of the flip-flop 109 is connected to a NAND gate 110. The other input of the NAND gate 110 is connected to the normally high audio-off line 71, while the output of the gate 110 is connected to one input of the gate 35. The flip-flop 103 and transistor 105 are used to control the potential on the silence line 107 in place of a simple switch, since contact bounce in a switch would cause several channels to be silenced.

In operation, when the silence switch 100 is momentarily operated, the flip-flop 103 changes state, turning off the transistor 105. The normally grounded silence line 107 will now appear at the voltage of the terminal 24 and the gate 108 for each unsilenced channel will have two high inputs and a grounded output. If the input to the flip-flop 109 which is connected to the output terminal 39 is grounded, the flip-flop 109 will change state. Since only one channel, at the most, will have'a grounded output terminal 39, only one of the flip-flops 1.09 will change state each time the silence switch 100 is operated. If the audio-off switch 95 is turned on, the gate 110 will have two high inputs and a low output and the gate 35 will now have a low input and a high output. The outputs of each of the gates 36, 37 and 38, and 40 will also change. The output 39 of the gate 38 will now be high and the associated switching amplifier 16 will be turned off. Since the output 41 of the gate 4.0 is now high, the gates 37 and 38' in the next lower priority channel will have high inputs and will be responsive to a condition sensed by the associated channel. if none of the lower priority channels are sensing conditions at the time a condition sensing channel is silenced, the output 41' of the lowest priority channel will become high and the master caution lamp driver 17 and the power supply 18 will be turned off.

Once the flip-flop 109 in a condition sensing channel is set by the momentary operation of the silence switch 100, it will remain set until a recall switch 111 is operated or the switch 31 is opened by the elimination of the sensed condition. When the switch 31 opens, the output of the gate 32 is grounded, grounding a preset terminal on the flip-flop 109 through a diode 112.

If the audio-off switch 95 is in the off position the silencing circuit will not operate. When the audio-off switch 95 is in the off position, the audio-off line 71 is grounded and each of the gates 110 in each logic channel will have a grounded input. Since the gate 110 has a grounded input from the audio-off switch 95, it cannot change state while the silence switch 100 is momentarily operated even though the flip-flop 109 changes state.

The operation of the recall switch 111 is shown in detail in FIG. 7. As in FIG. 6, diagonal marks are used to indicate leads which change state when the switch 111 is operated. A recall line 113 is connected from a normally open terminal on the switch 111 through parallel isolation diodes 114 to the preset terminal of each of the flip-flops 109. When the switch 111 is placed in the recall position the preset terminal on each of the flip-flops 109 is grounded and the output terminal of each flip-flop 109, which has been previously set by the silence switch 100, is set high. As long as the switch 31 continues to sense the occurrence of a condition, the lines having the diagonal marks will change state when the flipilop 109 is cleared and the output 39 for the NAN D gate 38 in the highest priority condition sensing channel will again become grounded, turning on the associated switching amplifier 16. It the condition is eliminated before the recall switch 111 is operated, the switch 31 will open and the gate 32 will have a grounded output. The grounded output of the gate 32 will ground the preset terminal of the flip-flop 109 through the isolation diode 112, resetting the flip-flop 109 in a manner similar to which it is reset by the recall switch 111.

The operation of the audio-test circuit is shown in detail in FIG. 8. When the test switch 72 is moved to the audio test" position, the normally high audio test line 33 is grounded. The gates 32 in each channel will now have a high output, the same as if each channel were sensing a condition. The logic circuit 12 for each channel will now be in a condition sensing state and the highest priority channel willhave a grounded output at the terminal 39. Thus, the switching amplifier 16 for the highest priority channel will be turned on. Each channel is sequentially tested, according to its priority ranking, by sequential operating the silence switch 100.

When the test switch 72 is moved to the lamp test position, the lamp test line 43 is grounded. The lamp test line 43 is connected to the NAND gate 42 in each logic circuit 12 to turn on each of the lamp drivers 13. All of the caution lamps 14 should glow when the test switch 72 is in the lamp test position, making it easy to identify a burnt out caution lamp -14.

Although it has not been shown in the block diagram of FIG. 1, an "end of message" signal may be recorded on each tape. An electronic switch (not shown) responsive to the end of message signal may be placed either in the audio switching amplifiers 16 or in-the audio amplifier and transducer 21 to block an audio output until the end of message signal is reached. Thus, the audio signal will start at the beginning of the recorded message on each tape cartridge 15.

It will be appreciated that other logic circuit arrangements may be used, and that various modifications and changes may be made in the remainder of the circuits without departing from the scope of the appended claims.

lclaim:

1. in a system having a plurality of condition sensing devices, each of the devices being responsive to the occurrence of a different condition to generate a signal an improved annunciator for warning a system operator of the occurrence of a sensed condition, said annunciator comprising, in combination:

a plurality of channels, each channel being connected to a different condition sensing device and each channel being assigned'a priority ranking;

means in each channel for generating an inhibit signal in response to a signal from the connected condition sensing device and in response to an inhibit signal from the next higher-priority channel;

a plurality of audio signal-generating devices;

means responsive to an inhibit signal from the lowest priority channel forsimultaneously actuating said audio signalgenerating devices;

a plurality of normally off switching amplifiers, one connected to each channel, each of said switching amplifiers having an input connected to the output of one of said audio signal-generating devices and each of said switching amplifiers having an output connected to a common terminal;

means for turning on the switching amplifier connected to the highest priority channel generating an inhibit signal;

means for audibly transmitting said common output of said switching amplifiers to the system operator; and manually actuated means for silencing the highest priority inhibit signal being generated and for causing the switching amplifier connected to the next highest priority inhibit signal being generated to turn on.

2. An improved annunciator for warning a system operator of the occurrence of a sensed condition, as defined in claim 1, including a memory means for each channel, means for setting each of said memory means when the associated channel has been silenced, and recall means for clearing said memory means, whereby, when said memory means is cleared, the highest priority channel connected to a device sensing a condition will again generate aninhibit signal.

3. An improved annunciator for warning a system operator of the occurrence of a sensed condition, as defined in claim 2, wherein each of said memory means will remain set only as long as the condition sensing device connected to the associated channel continues to sense a condition.

4. An improved annunciator for warning a system operator of the occurrence of asensed condition, as defined in claim 3, including means for testing said annunciator by simultaneously simulating all conditions sensed by the condition sensing device.

5. An improved annunciator for warning a system operator of the occurrence ofa sensed condition, as defined in claim 3, including a plurality of warning lamps, at least one of said warning lamps being associated with each of said channels, and means for energizing each of said warning lamps in response to a signal from the condition sensing device connected to the associated channel for each of said lamps.

6. In a system having a plurality of condition sensing devices, each of the devices being responsive to the occurrence of a different condition to generate a signal, an improved annunciator for warning a system operator of the occurrence of a sensed condition, said annunciator comprising, in combination:

means for assigning a priority ranking to each signal from the condition sensing devices;

a plurality of endless recording tapes, each of said tapes being associated with a different condition sensing device and each of said tapes having a message recorded upon it;

means for simultaneously driving each of said tapes wheni ever at least one of the sensed-conditions occurs;

a plurality of transducers, at least one transducer being associated with each of said tapes, each transducer having an electrical output corresponding to the recorded message on the associated tape whenever said tapes are driven;

a plurality of switching amplifiers, each of said switching amplifiers having an input connected to the output of a different transducer and each of said switching amplifiers having an output connected to a common output terminal;

means for turning on the switching amplifier for the tape and transducer associated with the highest priority condition sensing device generating a signal;

means connected to said common output terminal of said switching amplifiers for acoustically delivering to the system operator the output of said switching amplifiers; and

acknowledging means for turning off said switching amplifiers for the highest priority sensed condition and for simultaneously turning on the switching amplifier associated with the next highest priority sensed condition.

7. An improved annunciator for warning a system operator of the occurrence of a sensed condition, as defined in claim 6, including recall means for turning on the switching amplifier associated with the highest priority acknowledged sensed condition and for simultaneously turning off the switching amplifier associated with the highest priority unacknowledged sensed condition.

8. An improved annunciator for warning a system operator of the occurrence of a sensed condition, as defined in claim 7, including means for simultaneously simulating the occurrence of all conditions sensed by the sensing device to test the annunciator.

9. An improved annunciator for warning a system operator of the occurrence of a sensed condition, ad defined in claim 8, including a plurality of warning lamps, at least one of said warning lamps being associated with each of the condition sensing devices, and means for energizing each of said warning lamps whenever the associated device generates a signal.

10. An improved annunciator for warning a system operator of the occurrence of a sensed condition, as defined in claim 9, including a master caution lamp, and means for energizing said master caution lamp whenever one of said switching amplifiers is on.

Po-ws I UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,582 ,9 $9 Dated June 1, 1971 Inventor(s) S I/enaage Fors t It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 2, after the word "which", insert "is",

Column 2 line 32, the word "to", first occurrence, should be n".

Column 5, lines 60-61 delete "a signal in response to a different sensed condition, for example,",

Column 3, line 65, aiter the word "has", insert "a",

Column 7, line 6, the word "and" should be "or",

Column 7, line 66, the word "staged" should be "stated",

Column 8 line 28, the spelling of the word "to" should be 'two",

Column 8, line 4 after the word "channels", insert "are",

Column 9, line 24, after the number "57", delete the word and column 12, line 21 (Claim 8) the word "device" should The "devices",

Column 12 line 24 (Claim 9) correct the spelling of the word "as",

Signed and sealed this 26th "day of October 1 971 l. I (SEAL) Attest:

EDWARD M.FLETCHER,JR; ROBERT GOTTSCHALK Attssting Officer Acting Commissioner of Patents 

1. In a system having a plurality of condition sensing devices, each of the devices being responsive to the occurrence of a different condition to generate a signal an improved annunciator for warning a system operator of the occurrence of a sensed condition, said annunciator comprising, in combination: a plurality of channels, each channel being connected to a different condition sensing device and each channel being assigned a priority ranking; means in each channel for generating an inhibit signal in response to a signal from the connected condition sensing device and in response to an inhibit signal from the next higher priority channel; a plurality of audio signal-generating devices; means responsive to an inhibit signal from the lowest priority channel for simultaneously actuating said audio signalgenerating devices; a plurality of normally off switching amplifiers, one connected to each channel, each of said switching amplifiers having an input connected to the output of one of said audio signalgenerating devices and each of said switching amplifiers having an output connected to a common terminal; means for turning on the switching amplifier connected to the highest priority channel generating an inhibit signal; means for audibly transmitting said common output of said switching amplifiers to the system operator; and manually actuated means for silencing the highest priority inhibit signal being generated and for causing the switching amplifier connected to the next highest priority inhibit signal being generated to turn on.
 2. An improved annunciator for warning a system operator of the occurrence of a sensed condition, as defined in claim 1, including a memory means for each channel, means for setting each of said memory means when the associated channel has been silenced, and recall means for clearing said memory means, whereby, when said memory means is cleared, the highest priority channel connected to a device sensing a condition will again geneRate an inhibit signal.
 3. An improved annunciator for warning a system operator of the occurrence of a sensed condition, as defined in claim 2, wherein each of said memory means will remain set only as long as the condition sensing device connected to the associated channel continues to sense a condition.
 4. An improved annunciator for warning a system operator of the occurrence of a sensed condition, as defined in claim 3, including means for testing said annunciator by simultaneously simulating all conditions sensed by the condition sensing device.
 5. An improved annunciator for warning a system operator of the occurrence of a sensed condition, as defined in claim 3, including a plurality of warning lamps, at least one of said warning lamps being associated with each of said channels, and means for energizing each of said warning lamps in response to a signal from the condition sensing device connected to the associated channel for each of said lamps.
 6. In a system having a plurality of condition sensing devices, each of the devices being responsive to the occurrence of a different condition to generate a signal, an improved annunciator for warning a system operator of the occurrence of a sensed condition, said annunciator comprising, in combination: means for assigning a priority ranking to each signal from the condition sensing devices; a plurality of endless recording tapes, each of said tapes being associated with a different condition sensing device and each of said tapes having a message recorded upon it; means for simultaneously driving each of said tapes whenever at least one of the sensed conditions occurs; a plurality of transducers, at least one transducer being associated with each of said tapes, each transducer having an electrical output corresponding to the recorded message on the associated tape whenever said tapes are driven; a plurality of switching amplifiers, each of said switching amplifiers having an input connected to the output of a different transducer and each of said switching amplifiers having an output connected to a common output terminal; means for turning on the s witching amplifiers for the tape and transducer associated with the highest priority condition sensing device generating a signal; means connected to said common output terminal of said switching amplifiers for acoustically delivering to the system operator the output of said switching amplifiers; and acknowledging means for turning off said switching amplifiers for the highest priority sensed condition and for simultaneously turning on the switching amplifier associated with the next highest priority sensed condition.
 7. An improved annunciator for warning a system operator of the occurrence of a sensed condition, as defined in claim 6, including recall means for turning on the switching amplifier associated with the highest priority acknowledged sensed condition and for simultaneously turning off the switching amplifier associated with the highest priority unacknowledged sensed condition.
 8. An improved annunciator for warning a system operator of the occurrence of a sensed condition, as defined in claim 7, including means for simultaneously simulating the occurrence of all conditions sensed by the sensing device to test the annunciator.
 9. An improved annunciator for warning a system operator of the occurrence of a sensed condition, ad defined in claim 8, including a plurality of warning lamps, at least one of said warning lamps being associated with each of the condition sensing devices, and means for energizing each of said warning lamps whenever the associated device generates a signal.
 10. An improved annunciator for warning a system operator of the occurrence of a sensed condition, as defined in claim 9, including a master caution lamp, and means for energizing said master caution lamp whenever one of said switching amplifiers is on. 